speedo alarm?

[stnman]

Well, I've been lurking alot while I'm doing the build on my 71 GMC swb ;frame to pwdercoat next week! Walut media'd the whole thing-bla bla bla you get the picture , doing it right. went to Pamona today, hit up CCP for all the componits to do a 4-5 drop, still lots to do, but going back up now!
Now the good part. While my brother and I were there today-he's doing a 68 swb 4wd- I found a tach speedo/vacum etc, exellent restore, but it had someting I'dneverseen before, an alarm dial on the speedo face with a setting Knob to alert you if you speed. The guy does lots of 67-72 stuff and told me its a rare piece, did google search here and on www but could find no info. any one know just how rare this is?

Thanks for any info! Stoney L.A./ yes,I got it!